For many years the commonly used lamp shade has consisted of little more than a diffusing cylinder surrounding a compact light source, such as a light bulb. The shade has been regarded as a functional necessity to cover the excessive direct horizontal glare from the light source, usually called disability glare. Shades have sometimes been provided with ornamentation in the interest of aesthetics. Lamp shades for the table lamps, floor lamps and swag lamps, known in the lighting industry as portable lamps, have little or no optical design to improve the quality and efficiency of the light produced.
Conversely, the commercial lighting fixture industry has become very sophisticated in the development of diffusers for recessed and surface mounted lighting fixtures. Precise definition of direct horizontal glare control has been achieved, and is comparatively measured in terms of "Visual Comfort probability" (VCP). Also there has been acceptance of a measure of lighting quality with respect to reflected glare in terms of "Equivalent Sphere Illumination" (ESI). Fixtures are no longer rated by raw lamp lumen output, but are part of an overall lighting system design that maximizes the usefulness of the light to reduce the energy input.
The costs of energy, and indeed legislation that limits the wattage allowable per square foot of building, has increased the use of "Task Lighting" in commercial and industrial applications, applying relatively high light levels to desks while reducing the light level in surrounding room areas. In order to provide adequate task illumination, a typical task light now consists of a four foot long fluorescent fixture that is horizontally mounted on vertical supports on a desk. The net result is usually excessively high illumination levels and reflected glare on the desk in an ugly installation.
The purpose of the present invention is to provide a highly efficient lamp shade that will permit the use of portable lamps to create energy efficient and optically correct lighting for improved visual performance in both residential and commercial lighting. A second purpose of the present invention is to provide a decorative lamp shade that is an attractive addition to portable lamps, such as table, floor or swag lamps. A third purpose of the present invention is to provide effective control of both horizontal and reflected glare from the light source.